This invention relates to an internal combustion engine and more particularly to an improved, direct cylinder injected engine.
In the interest of improving the performance of an engine both in terms of specific output, fuel economy, and exhaust emission control, direct cylinder injection offers significant advantages. One advantage of direct cylinder injection is that if it can be combined with so-called "stratification" the fuel economy and exhaust emission control can be substantially improved.
One difficulty in obtaining optimum fuel economy and exhaust emission control is the problem of initiating combustion in the combustion chamber. Obviously, a stoichiometric charge must be present at the gap of the spark plug at the time of firing or a combustion will not begin.
With conventional engines, in order to ensure the presence of a stoichiometric mixture at the spark plug gap at the time of firing, the entire cylinder is charged with a stoichiometric mixture. This obviously results in the introduction of more fuel than is required to produce the specific output at low and mid-range speeds and loads.
Thus, it has been proposed to employ some form of system wherein the fuel charge is stratified in the combustion chamber, at least under some running conditions. It is not desirable to provide total stratification under all running conditions for a reason which will be described.
In order to provide stratification that is effective, it is necessary to provide at least a patch of fuel air mixture that has a stoichiometric ratio. However, the introduction of such a patch of fuel is only a small part of the problem. It must be ensured that the stoichiometric patch of fuel is present at the spark gap at the time of firing. This must be assured under all running conditions when stratification is desired.
Although certain features may be employed to improve or insure stratification, the charge in the entire combustion chamber should be homogenous when operating at high speeds and high loads. If this is not done, then maximum power cannot be achieved. Many forms of stratification do not permit the attainment of a homogenous mixture at the running conditions where it is desired.
Also, stratification may be achieved through the use of pre-chambers or other devices which significantly complicate the configuration of the combustion chamber and which can reduce performance under some running conditions. For example, many forms of stratified charge engines that employ pre-chambers have high pumping losses.
Added to the problems aforenoted, is the actual physical configuration of the combustion chamber and the layout of those components which are associated with it. If the engine is provided with direct cylinder injection and spark ignition, it is desirable that the spark plug gap be disposed in an area close to the center of the combustion chamber volume at the time of firing. This generally dictates a central positioning of the spark plug in the cylinder head. Where the engine is provided with multiple valves in order to improve performance, then little space is left for the positioning of the fuel injector.
One proposed position for the fuel injector is at a side of the combustion chamber and generally adjacent the intake valves. Frequently, it is desirable to position the fuel injector between the intake valves, as has been proposed in the prior art. However, this greatly complicates the goal of achieving stratification.
Therefore, it has been proposed in engines having a configuration that employs at least a pair of intake valves, a centrally positioned spark plug and a fuel injector at the side of the combustion chamber and between the intake valves, a bowl and piston configuration. Various shapes of bowls have been proposed for the combustion chamber and various arrangements wherein the fuel is sprayed into the bowl and the bowl cooperates in the achievement of stratification. One difficulty with most of these arrangements, if not all of them, is that it is difficult to achieve stratification over a wide range of running conditions. Furthermore, the bowl configuration can result in unburned fuel in the combustion chamber under some running conditions.
It is, therefore, a principal object of this invention to provide an improved direct cylinder injected engine.
It is a still further object of this invention to provide an improved combustion chamber and induction system arrangement for a direct cylinder injection wherein stratification can be achieved without compromising the configuration of the combustion chamber or the location of the components.
It is a yet further object of this invention to provide an improved direct cylinder injected engine utilizing multiple valves, a centrally positioned spark plug and a side mounted injector wherein stratification can be achieved without compromising the configuration of the combustion chamber without requiring complicated bowl and piston designs.